THE SKELETON OF THE BLACK BASS. 



319 



As the accompanying figure, shown in plate 44, of the skeleton of this bass is 

 reproduced from a photograph of a carefully dissected and dried skeleton, it will be 

 obseryed that a little ligamentous material is remaining, and some of the bony lin- 

 rays and spines are very slightly uuparallel, but this faiit will lead no one astray, as 

 It is quite evident which bones have become so while the skeleton was drying. The 

 arrangement of these osseous Jin-rays and interspinous bones practically agrees with 

 those elements as we have long known them to exist iii all ordinary bony fishes, as in 

 the common yellow perch for example {Perca). 



The skeleton of the tail in Micropterus is of the typical homocercal type, and devel- 

 ops a very completely ossified vroslylc, directed upward and backward at an angle 

 of about 45 degrees, with a markedly straight vertebral column, as is plainly to be 

 seen in plate 44. The osseous expanded portion of the tail is in the vertical plane, and 

 is thus modified in order to give support to the bony rays of the caudal fin. Possibly 



Syo.c 



Ast 



Fig. 8.— Outer aspect of part of shoulder girdle and pector&l fin ofilf. salmoides. Natnralsize and drawn 

 by tbe author from his own dissections. P«., proscapular, with other lettering the same as in fig-'^ 



7 



I may formerly have considered that this expanded portion contained ttoo vertebrw, 

 and it may. In this case the count for thirty-two vertebrte in the column would be 

 correct; but in the reckoning given above this part is omitted and only the vertebrae 

 taken into consideration which possess the true form of those bones. 



These terminal modified vertebrae are known as the hypural plates, and they are very 

 broad and perfect in M. salmoides. The caudal osseous fin-rays are ligamentously 

 attached to the posterior margins of the hypural plates in the simple manner seen 

 among all ordinary teleostean fishes generally. Both above and below, the 29th and 

 30th vertebra} have narrow and elongated hypural plates springing from them, and 

 the 29th has the hsemal and neural spines in addition thereto, but these last are absent 

 in the 30th vertebra. These hy[)ural spines support distally the outer and very 

 rudimentary fin-rays of the tail. Counting from before backward, it is the third 

 hypural plate upon either side that developed the urostyle spoken of above, and which 



